This invention relates to asynchronous transfer mode (ATM) signal processor systems and more especially it relates to such systems for ATM data transmission wherein the transmission comprises a number of cells which are transmitted successively and which in combination define a data package or frame wherein the last cell of the package is characterized by an identifying data code.
When a plurality of transmissions are made each relating to a different data package, the cells of the various transmissions are multiplexed or interleaved to provide a serial data stream. It will be appreciated that ATM data traffic is inherently bursty in nature, and in order to accommodate widely varying data rates arriving at a server, a serial buffer store is normally provided via which the server is fed with the serial data stream. Since in times of heavy traffic the capacity of the buffer store may be inadequate, the buffer store is arranged to have an in-built threshold capacity beyond which data is discarded and lost whereby re-transmission is required.
It will be appreciated that when a cell is discarded, the data package of which it forms a part is corrupted such that subsequently transmitted cells which form part of the same data package are useless. As the buffer store empties, however, useless subsequently received cells relating to the corrupted data package may nevertheless be stored in the buffer so as to occupy buffer storage capacity which might be more fruitfully used. Thus, data transmission efficiency is reduced.